In many cases, broadband receivers are used to receive signals from several sources. Frequently, one particular signal needs to be selected from among the signals received. Alternatively, more than one signal need to be combined to form a composite signal. Different signals may need to be combined for transmission together over a shared medium, such as coaxial cable within a home. For example, in a home entertainment network, signals may be received from various sources, such as satellite dishes, MoCA (Multimedia over Coax Alliance) networks, or cable television feeds. In some such cases, these signals must be combined for communication over a common medium, such as a coaxial cable that allows components within the home entertainment network to communication with one another.
FIG. 1 is a simplified block diagram of a signal selector 100. A first single pole-triple throw switch 102 is used to select one of three filters 104, 106, 108 to be connected to an input 110. A second single pole-triple throw switch 112 selects the output of the selected filter 104, 106, 108 to be coupled to the output 114 of the signal combiner 100. The first filter 104 has relatively low band pass frequency response that extends from a first frequency of approximately f1 to a second frequency of approximately f2. The second filter 106 has a relatively high band pass frequency response that extends from a third frequency of approximately f3 to a fourth frequency of approximately f4. The third filter 108 has a relatively wide bandpass frequency response that extends from the first frequency of approximately f1 to approximately the fourth frequency of f4. Accordingly, by setting the switches appropriately, the signals with a frequency of f1 to f2 that are present at the input 110 can be selected to be coupled through to the output by selecting the first position in both the input switch 102 and the output switch 114. Likewise, by setting the input and output switches 102, 114 to the second position, signals with a frequency of f3 to f4 that are present at the input 110 can be selected to be coupled through to the output. Finally, by setting the input and output switches 102, 114 to the third position, signals with a frequency of f1 to f4 that are present at the input 110 can be selected to be coupled through to the output.
While this arrangement works well, the fact that it requires two single pole, triple throw switches causes the selector 100 to have a relatively high loss from the input 110 to the output 114. Furthermore, the two switches add distortion to the signal. Therefore, there is presently a need for a low loss signal combiner that can select between different filters inexpensively.
In the context of a home entertainment network, selection of signals carried on several different frequency bands is necessary. FIG. 2 is a simplified block diagram of a universal MoCA diplexer 200. The diplexer 200 has six filters 202, 204, 206, 208, 210, 212. Three of the filters 202, 204, 206 are used to select satellite television signals and MoCA signals. Another two filters 208, 210 are used to select MoCA. The MoCA band is selected based upon whether the frequency band will be shared by satellite television or cable television signals. When satellite signals are present, MoCA signals are modulated on the E-band (500 MHz to 600 MHz) or F-band (675 MHz to 850 MHz). When used with cable television signals, MoCA is typically modulated on the D-band (1150 MHz to 1500 MHz). The sixth filter 212 is used to select cable television (CATV) signals. Two multi-throw switches 214, 216 are used to select which filter from among the five filters 202, 204, 206, 208, 210 is to be coupled to the output 218 and which filter is to be coupled to the input 220. A single pole, single throw switch 222 is used to connect the input 220 to the CATV filter 212.
The use of multi-throw switches increases the loss in the circuit substantially. Therefore, there is a need for a universal diplexer that can select from among several frequency bands without encountering the substantial losses associated with multi-throw switches.